address review comments

- more inline documentation
 - don't explicitly specify audience
 - approver is optional in `generate_key`
 - ADD -> RUN for better caching of jwtproxy

config.py

@@ -289,8 +289,14 @@ class DefaultConfig(object):
     'API_TIMEOUT_SECONDS': 10,
     'API_TIMEOUT_POST_SECONDS': 480,
   }
+
+  # JWTProxy Settings
+  # The address (sans schema) to proxy outgoing requests through the jwtproxy
+  # to be signed
   JWTPROXY_SIGNER = 'localhost:8080'
-  JWTPROXY_AUDIENCE = 'https://quay.io:443'
+  # The audience that jwtproxy should verify on incoming requests
+  # If None, will be calculated off of the SERVER_HOSTNAME (default)
+  JWTPROXY_AUDIENCE = None
 
   # Torrent management flags
   FEATURE_BITTORRENT = False